Various surgical techniques have been developed to counteract ischemic conditions of the heart, including coronary bypass grafts, angioplasty and for patients who are not suitable candidates for these procedures, or in conjunction with these procedures, transmyocardial revascularization (TMR). In TMR generally, the surgeon creates many narrow channels of approximately one millimeter width that span from an opening at the endocardial surface of a ventricle of the heart, preferably the left ventricle, into the myocardium and then terminating before the epicardial surface. The surgeon generally uses laser to create the channels by either accessing the endocardium through a percutaneous route or the epicardium through an incision into the chest wall. The pressure within the left ventricle at systole forces oxygenated blood into the channels and consequently oxygenates the ischemic myocardium of the left ventricle. Methods of TMR using laser, a combination of laser and mechanical, and solely mechanical apparatus have been disclosed in the prior art, including United States patents such as U.S. Pat. Nos. 4,658,817 (Hardy), 5,125,926 (Rudko, et al) and 5,380,316 and 5,389,096 (Aita, et al) and also more recently in co-pending applications Ser. No. 08/607,782 and Ser. No. 08/713,531.
The percutaneous method does not require the epicardium to be perforated. The surgical method through incision into the chest wall does require perforation of the epicardium to create channels through the myocardium and endocardium which may result in increased peri- and post-operative bleeding. Recent methods described in pending applications Ser. Nos. 08/607,782 abd 08/713,531, however, provide for initial mechanical piercing of the epicardium prior to ablation of myocardial and endocardial tissue by laser which reduces bleeding from the channels into the chest cavity.
A current limit of TMR in revascularizing myocardial tissue includes post-operative closure of a significant proportion of the channels. With little success, attempts have been made by practitioners to maintain the patency of the lumen of the channels through administration of appropriate pharmacologically active compounds. Maintaining a sufficient concentration of such compounds within the channels is very difficult considering the channels are exchanging circulation with the high blood volume interchange of the left ventricle.
TMR's effectiveness in revascularizing ischemic myocardial tissue results not only from the introduction of oxygenated blood into the myocardium through the created channels, but through the increase in angiogenesis in the myocardial tissue surrounding the channels secondary to localized immune-mediated responses. Co-pending application Ser. No. 08/664,956 describes the advantage of creating channels and pockets intramyocardially in stimulating angiogenesis of the myocardium by using laser supplemented optionally with mechanical means. The pockets or channels do not need to be patent at the endocardial surface at creation nor remain patent over time for the angiogenesis stimulation to be effective. The stimulation of angiogenesis occurs through localized immune mediated response to the tissue trauma resulting in an influx of blood borne growth and healing factors and stimulation of capillary growth surrounding the pockets or channels. The oxygenation of myocardial tissue and the functioning capacity of the heart are thereby increased significantly. It is desireable, therefore, to provide an effective concentration of pharmacologically active angiogenic compounds to the myocardium to stimulate angiogenesis on a supplementary or independent basis for the same drug delivery problems as discussed above.
Methods have been disclosed in certain of the above cited art for removing myocardial tissue through laser emission ablation or mechanical cutting techniques to create channels and/or pockets for myocardial revascularization purposes. A noted advantage of using a mechanical cutting tool over the laser method is the ability to cut and remove a discrete piece of tissue. In addition, less bleeding occurs with the use of mechanical as verses laser perforation of the epicardium.
An advantage of using laser over the mechanical method is the reduction in force necessary to pierce the surface and advance through the body of a muscle, and more particularly, piercing the epicardium and advancing through myocardial tissue. The reduction in force allows the surgeon greater ease and control over the procedure. An additional advantage of laser over mechanical surgery is that thermal as compared to mechanical trauma of tissue results in less peri- and post-operative bleeding, less consequential tissue tearing with consequential post-operative fibrous scarring, and potentially greater post-operative immune-mediated reactive angiogenesis.
Methods have been disclosed in certain of the above cited art for synchronizing the laser emission of TMR with the heart beat (as measured by EKG) of the heart (U.S. Pat. No. 5,125,926 (Rudko, et al). These synchronization efforts were made in the attempt to time the emission of the laser with the electrically quiet period of the heart to reduce the occurence of arrhythmias. The peaks of the EKG waves reflect the electrical conductance of the heart, however, and therefore do not directly match the actual contraction of the musculature of the heart. Methods have not been disclosed for synchronizing, directly or indirectly, pocket formation with the contraction of the heart.
The above methods and apparatus and discoveries to date have not provided for concomitant administration of pharmacologically active substances to the channels and/or pockets at their creation. It is therefore desirable to provide an apparatus and method for making distinct pockets within muscle tissue, and in particular, the myocardium, for controllable drug delivery for purposes, among others, of increasing the patency of myocardial channels and/or increasing angiogenesis in the surrounding myocardial tissue. It is further desirable to provide an apparatus and method that simultaneously combines the use of laser and mechanical means to maximize the advantages and minimize the disadvantages of each. Such an apparatus and method is easily controlled by a surgeon, administers moderate thermal damage reducing reactive bleeding and fibrous scarring and increasing reactive immune-mediated localized angiogenesis, cleanly removes all excised tissue, and concomitantly optionally delivers substances or inserts containing pharmacologically active compounds into the formed pocket. It is also further desired to provide an apparatus and method for directly synchronizing the timing of the pocket formation with the contraction of the heart.